Flexible grid and predominantly concrete mat employing same

ABSTRACT

A predominantly concrete mat comprises a concrete slab having two longitudinal edges and two transverse edges and having relatively thicker portions and relatively thinner portions, which include relatively thinner portions among the longitudinal and transverse edges, and a flexible grid embedded in the concrete slab. The flexible grid, which is polymeric, is molded so as to have longitudinally extending members and transversely extending members. End portions of specific ones but not all of the longitudinally extending members of the flexible grid extend into and nearly or completely through the relatively thinner portions along the transverse edges of the concrete slab. End portions of specific ones but not all of the transversely extending members of the flexible grid extend into and nearly or completely through the relatively thinner portions along the longitudinal edges of the concrete slab.

TECHNICAL FIELD OF THE INVENTION

This invention pertains to a flexible grid, which is useful to connectconcrete blocks of a predominantly concrete mat, and to a predominantlyconcrete mat employing such a flexible geogrid.

BACKGROUND OF THE INVENTION

A flexible, molded, polymeric grid and a predominantly concrete matemploying the flexible grid are disclosed in U.S. Pat. No. 7,048,469 B1,the disclosure of which is incorporated by reference herein. Asdisclosed therein, the flexible grid has longitudinally extendingmembers and transversely extending members and is embedded in a concreteslab having relatively thicker portions and relatively thinner portions.The relatively thicker portions define blocks, which are connected bythe relatively thinner portions. The longitudinally and transverselyextending members of the flexible grid connect the blocks to oneanother, when the concrete slab is broken along the relatively thinnerportions, whereby the predominantly concrete mat is articulated.

As disclosed in U.S. Pat. No. 7,048,469 B1, the concrete slab hasrelatively thinner portions along its longitudinal and transverse edges.Consequently, if the flexible mat is not approximately centered when theconcrete slab is made, one of the members bounding the flexible mat,along one of its longitudinal and transverse edges, can become embeddedwithin the relatively thinner portion along the corresponding edge ofthe concrete slab and can weaken the same portion sufficiently for theweakened edge to crumble. Similarly, the relatively thinner portionsmeeting at a corner of tje concrete mat can be so weakened.

In an earlier form, an articulated, predominantly concrete mat isdisclosed in U.S. Pat. No. 5,108,222, the disclosure of which isincorporated by reference herein. In an improved form, an articulated,predominantly concrete mat is disclosed in U.S. Pat. No. 6,612,776 B1,the disclosure of which is incorporated by reference herein. Asdisclosed in these patents, such a mat has numerous uses in retardingearth erosion due to wind, water, or both and in lining a driveway, aparking area, or an emergency roadway.

SUMMARY OF THE INVENTION

This invention provides a flexible grid adapted to be embedded in aconcrete slab having two longitudinal edges and two transverse edges andhaving relatively thicker portions and relatively thinner portionsincluding relatively thinner portions among the longitudinal andtransverse edges. The flexible grid has longitudinally extending membersand transversely extending members. The longitudinally and transverselyextending members meet at nodes.

As provided by this invention, specific ones of the longitudinallyextending members have end portions extending beyond the end portions ofthe others of the longitudinally extending portions and beyond whicheverof the transversely extending members are endmost. Moreover, specificones of the transversely extending members have end portions extendingbeyond the end portions of the others of the transversely extendingportions and beyond whichever of the longitudinally extending membersare endmost.

In one contemplated embodiment of this invention, wherein all of thelongitudinally extending members have end portions extending beyondwhichever of the transversely extending members are endmost, while theend portions of the specific ones of the longitudinally extendingmembers extend further than the other ones of the longitudinallyextending members beyond whichever of the transversely extending membersare endmost. Moreover, all of the longitudinally extending members haveend portions extending beyond whichever of the transversely extendingmembers are endmost, while the end portions of the specific ones of thetransversely extending members extend further than the other ones of thetransversely extending members beyond whichever of the longitudinallyextending members are endmost.

This invention also provides a predominantly concrete mat comprising aconcrete slab having two longitudinal edges and two transverse edges andhaving relatively thicker portions and relatively thinner portions,which include relatively thinner portions among the longitudinal andtransverse edges, and a flexible grid, as described above. The flexiblegrid is embedded in the concrete slab so that the end portions of thespecific ones of the longitudinally extending members of the flexiblegrid extend into and nearly or completely through the relatively thinnerportions along the transverse edges of the concrete slab and so that theend portions of the specific ones of the transversely extending membersof the flexible grid extend into and nearly or completely through therelatively thinner portions along the longitudinal edges of the concreteslab.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, isometric view of a concrete slab, in which aflexible grid embodying this invention and defining flexible membersextending longitudinally and transversely is embedded.

FIG. 2, on a smaller scale, is a fragmentary, schematic plan of aninjection mold, in which the flexible grid illustrated in FIG. 1 isbeing molded. FIG. 3 is a greatly enlarged, sectional detail taken alongline 3-3 of FIG. 4, in a direction indicated by arrows. FIG. 4, on asimilar scale, is a fragmentary plan of a portion of the flexible grid.

FIG. 5, on a larger scale, is a fragmentary cross-section of a castingmold, in which the concrete slab is being cast in an invertedorientation, as seen after an upper portion of the casting mold has beenraised, a lower portion of the casting mold has been filled partiallywith a concrete mix, and the flexible grid has been placed on theconcrete mix.

FIG. 6, on a similar scale, is a fragmentary, isometric view of anarticulated, predominantly concrete mat, as made from the concrete slabhaving the embedded grid, when the concrete slab having the embeddedgrid is broken along thin areas so as to define concrete blocks, whichare connected to one another by the flexible members of the flexiblegrid.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

As illustrated in FIG. 1, an intermediate article 10 in the manufactureof an articulated, predominantly concrete mat, which is similar to thearticulated, predominantly concrete mat disclosed in U.S. Pat. No.7,048,469 B1, supra, comprises a rectangular, concrete slab 20 and aflexible grid 30, which is embedded in the concrete slab 20.

As illustrated in FIG. 5, when the concrete slab 20 is cast in a castingmold 60, which has a lower portion 62 and an upper portion 62, the lowerportion 62 of the casting mold 60 is filled partially with a concretemix M, onto which the flexible grid 30 is placed. Thereupon, the lowerportion 60 is filled completely with the concrete mix M, whereby theflexible grid 30 is embedded in the concrete mix M. Thereupon, the upperportion 62 is lowered so as to close the casting mold 60, in which theconcrete mix M is cured.

The concrete slab 20 is cast, in an inverted orientation relative to itsillustrated orientation, so as to have relatively thinner portions 22extending longitudinally and transversely and so as to have relativelythicker portions 24, which are separated from one another by therelatively thinner portions 22. The relatively thinner portions 22include relatively thinner portions 22 a along the longitudinal edges ofthe concrete slab 20 and relatively thinner portions 22 b along thetransverse edges of the concrete slab 20.

As illustrated in FIG. 7, the concrete slab 20 is breakable along therelatively thinner portions 22, so that the relatively thicker portions24 become discrete, concrete blocks 40 connected to one another byflexible members 32 of the flexible grid 30, which remains embedded inthe respective blocks 40, whereby an articulated, predominantly concretemat 50 is provided. The flexible members 32 meet and are joined at nodes34. Preferably, the flexible members 32 have circular cross-sections,but the flexible members 32 may have oval, rectangular, or othercross-sections.

So as to facilitate breaking of the concrete slab 20 along therelatively thinner portions 22, the concrete slab 20 has spaced holes,which include holes having circular mouths and holes having squaremouths, along the relatively thinner portions 22. The relatively thinnerportions 22 may be sufficiently thin to enable the concrete slab 20 tobe thus broken by its own weight if and when the concrete slab 20 islifted from its edges. Alternatively, the concrete slab 20 may be thusbroken by a person wielding a suitable tool, such as an adze.

As exemplary dimensions, all of which are approximate, the concrete slab20 may have a width of twenty-four inches and a length of forty-eightinches, the relatively thinner portions 22 may have a thickness ofthree-eights inch, the relatively thicker portions 24 may have athickness of one inch, the flexible geogrid 30 may have two inch squareopenings, which are defined by the flexible members 32, and therespective blocks 40 may be four inches square.

The flexible grid 30 may be injection molded, as illustratedschematically in FIG. 2, so as to have longitudinally extending members32 and transversely extending members 34. The longitudinally andtransversely extending members 32, 34, meet at nodes 36, which arespaced precisely and uniformly (e.g. by two inches) from one another,both longitudinally and transversely.

As illustrated in FIG. 2 and other views, all of the longitudinallyextending members 32 have end portions 36 extending beyond whichever ofthe transversely extending members 34 bound the flexible grid 30.Moreover, specific ones of the longitudinally extending members have endportions 36 a extending further than the end portions 36 of the othersof the longitudinally extending portions 32 and further than thetransversely extending members 34 at the boundaries of the flexible grid30.

As illustrated in FIG. 2 and other views, all of the transverselyextending members 34 have end 38 portions extending beyond whichever ofthe longitudinally extending members 32 bound the flexible grid 30.Moreover, specific ones of the transversely extending members 34 haveend portions 38 a extending further than the end portions 38 of theothers of the transversely extending portions 34 and further than thelongitudinally extending members 32 at the boundaries of the flexiblegrid 30.

As illustrated in FIG. 2 and other views, the specific ones of thelongitudinally extending members 32 having the end portions 32 aextending further are separated from one another and from thetransversely extending members 34 at the boundaries of the flexible grid30 by one or more of the longitudinally extending members 32. Moreover,the specific ones of the transversely extending members 34 having theend portions 34 a extending further are separated from one another andfrom the longitudinally extending members 32 at the boundaries of theflexible grid 30 by one or more of the transversely extending members34.

As illustrated in FIG. 2 and FIG. 5, the end portions 32 a extendingfurther extend into and nearly or completely through the relativelythinner portions 22 a along the longitudinal edges of the concrete slab20. Moreover, the end portions 34 a extending further extend into andnearly or completely through the relatively thinner portions 22 b alongthe transverse edges of the concrete slab 20.

1. A flexible grid adapted to be embedded in a concrete slab having twolongitudinal edges and two transverse edges and having relativelythicker portions and relatively thinner portions, which includerelatively thinner portions among the longitudinal and transverse edges,the flexible grid having longitudinally extending members andtransversely extending members, the longitudinally and transverselyextending members meeting at nodes, wherein specific ones of thelongitudinally extending members have end portions extending beyond theend portions of the others of the longitudinally extending portions andbeyond whichever of the transversely extending members are endmost, andwherein specific ones of the transversely extending members have endportions extending beyond the end portions of the others of thetransversely extending portions and beyond whichever of thelongitudinally extending members are endmost.
 2. The flexible grid ofclaim 1, wherein all of the longitudinally extending members have endportions extending beyond whichever of the transversely extendingmembers are endmost, while the end portions of the specific ones of thelongitudinally extending members extend further than the other ones ofthe longitudinally extending members beyond whichever of thetransversely extending members are endmost, and wherein all of thelongitudinally extending members have end portions extending beyondwhichever of the transversely extending members are endmost, while theend portions of the specific ones of the transversely extending membersextend further than the other ones of the transversely extending membersbeyond whichever of the longitudinally extending members are endmost. 3.The flexible grid of claim 1, wherein the specific ones of thelongitudinally extending members are separated from one another and fromwhichever of the transversely extending members are endmost by one ormore of the longitudinally extending members, and wherein the specificones of the transversely extending members are separated from oneanother and from whichever of the longitudinally extending members areendmost by one or more of the transversely extending members.
 4. Theflexible grid of claim 2, wherein the specific ones of thelongitudinally extending members are separated from one another and fromwhichever of the transversely extending members are endmost by one ormore of the longitudinally extending members, and wherein the specificones of the transversely extending members are separated from oneanother and from whichever of the longitudinally extending members areendmost by one or more of the transversely extending members.
 5. Apredominantly concrete mat comprising a concrete slab having twolongitudinal edges and two transverse edges and having relativelythicker portions and relatively thinner portions, which includerelatively thinner portions among the longitudinal and transverse edges,and a flexible grid according to claim 1, 2, 3, or 4, wherein theflexible grid is embedded in the concrete slab so that the end portionsof the specific ones of the longitudinally extending members of theflexible grid extend into the relatively thinner portions along thetransverse edges of the concrete slab and so that the end portions ofthe specific ones of the transversely extending members of the flexiblegrid extend into the relatively thinner portions along the longitudinaledges of the concrete slab.
 6. A predominantly concrete mat comprising aconcrete slab having two longitudinal edges and two transverse edges andhaving relatively thicker portions and relatively thinner portions,which include relatively thinner portions among the longitudinal andtransverse edges, and a flexible grid according to claim 1, 2, 3, or 4,wherein the flexible grid is embedded in the concrete slab so that theend portions of the specific ones of the longitudinally extendingmembers of the flexible grid extend into and nearly or completelythrough the relatively thinner portions along the transverse edges ofthe concrete slab and so that the end portions of the specific ones ofthe transversely extending members of the flexible grid extend into andnearly or completely through the relatively thinner portions along thelongitudinal edges of the concrete slab.